We are writing as environmentalists, conservationists and climate scientists to applaud your country’s commitment to fighting climate change through energy policy. Spain has been at the forefront of generations of low-carbon energy technologies, from nuclear plants in the 1960s to the world’s most advanced and ambitious solar energy plants in the 1990s and 2000s.

In light of these achievements, we are also writing to express our alarm at your decision to close a nuclear plant and to urge you to keep and expand your remaining nuclear plants.

The Spanish nuclear program was once rapidly displacing fossil fuels in the country’s energy mix. Spain demonstrated in the 1970s and 80s that decarbonization with growth is possible. However, the nuclear moratorium enacted in 1983 halted the creation of enough nuclear power to replace all of the coal it now burns for electricity.

Few nations have done more than Spain to explore the possibilities and limitations of various types of low-carbon energy. Spain boasts an unusually mixed set of technologies supplying its electricity, with more than 10 percent of its electricity coming from low-carbon wind, hydro, and nuclear. Solar contributes another 5 percent. However, over 40 percent of Spain’s electricity last year was provided by coal and natural gas.

The loss of the Santa Maria de Garoña nuclear plant was a significant step backwards for Spain’s climate goals. The fossil fuels used to replace the plant’s power will put about 2 million tonnes of carbon emissions into the atmosphere each year, the carbon equivalent of almost a million new cars on the road in Spain. Despite former minister Álvaro Nadal’s claim that closing the plant would have no effect on the nation’s power grid, closing the plant eliminates clean power that could have fueled 1.8 million electric vehicles.

Any further reduction in Spain’s nuclear generation will likewise increase fossil fuel generation and pollution given the low capacity factors and intermittency of solar and wind. Germany is a case in point: its emissions have been largely unchanged since 2009 due to nuclear plant closures, with increases in 2015, 2016, and 2017. If the electricity from Spain’s surviving nuclear fleet is replaced by its abundant natural gas and coal plant capacity, carbon emissions will increase by about 32 million tonnes CO₂ per year, or the equivalent of adding 14.5 million new cars to Spanish roads.

In addition to making its emissions reduction goals more difficult to meet, Spain also risks further increasing its electricity prices as nuclear closes. Though Spain’s electricity costs are now among the highest in Europe, they were below average before 2009. The need to pay for tens of billions of dollars for renewable energy caused this rapid rise in cost. This experience is shared by other countries in Europe that are eliminating nuclear. For example, Germany spent 24.3 billion euros above market price in 2017 for its renewable energy feed-in tariffs yet will widely miss its 2020 emission reduction goals. Spain can learn from Germany’s failure to keep nuclear plants in operation.

For Spain’s future, the next step to combat climate change and improve air quality is to increase clean electricity from non-fossil sources and massively reduce fossil fuels used in heating and the transportation sector. If Spain is to achieve these goals, nuclear power must play a central role once again.